Phase II trial of nab-paclitaxel as first-line therapy of hormone refractory metastatic prostate cancer (HRPC)

Abstract

5152 Background: Many patients with hormone refractory prostate cancer have poor tolerance to treatment. Docetaxel chemotherapy was shown to improve survival but has substantial toxicity, requires steroid administration, may cause poorly reversible neuropathy and requires long infusion times, all limiting its use. Nab-paclitaxel, an albumin-bound nanopaticle form of paclitaxel, delivers paclitaxel without steroids, requires only 30 minutes infusion time and has favorable toxicity profile that may be more tolerable but effective in patients with prostate cancer. The goal of this study was to evaluate the efficacy and toxicity of nab-paclitaxel in first line chemotherapy of men with castration resistant prostate cancer. Methods: nab-paclitaxel was given iv100 mg/m2 weekly x 3 of 4 weeks cycles. Main eligibility criteria include: hormone refractory metastatic prostate cancer, no prior chemotherapy, performance status 0–2. Primary endpoint was efficacy based on prostate-specific antigen (PSA) response. PSA response was PSA decrease of >50%, progressive disease (PD) was PSA increase of >25%, stable disease (SD) was <25% PSA increase or <50% decrease sustained longer that 8 weeks. Results: There are 38 patients enrolled, 35 were evaluable for response. Median age was 71 years old (range 57–86). One patient discontinued the treatment after 1 infusion due to toxicity (elevated ALT). PSA response was seen in 9 (25%) patients and SD in 15 patients (43%), with an overall response rate of 25% and clinical benefit of 68%. Seven patients received treatment for ≥ 6 months with minimal toxicity (range 6–10 months). Grade 3 related hematologic toxicity was reported in 7 (18%) patients (4 anemia, 4 neutropenia), grade 3 related non-hematologic toxicity was reported in 6 patients (1 hypokalemia, 1 muscle weakness, 2 fatigue, 1 fever, 1 neuropathy, 1 ALT elevation). Conclusions: Nab-paclitaxel has activity in patients with metastatic hormone refractory prostate cancer. This regimen was well tolerated, and may be useful in patients who are not suitable candidates for docetaxel based therapy. [Table: see text]